Note 5 - Investments In and Advances to Real Estate Joint Ventures - Joint Venture Investments Accounted for Under the Equity Method, Debt Details (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Mortgage and notes payable		$ 1,657.1	$ 1,541.0
Prudential Investment Program [Member]
Mortgage and notes payable		$ 491.8	$ 495.8
Weighted average interest rate		1.95%	2.05%
Weighted average remaining term (Month)	[1]	46 months 15 days	37 months 6 days
KIR [Member]
Mortgage and notes payable		$ 508.4	$ 536.9
Weighted average interest rate		3.11%	3.87%
Weighted average remaining term (Month)	[1]	24 months 27 days	25 months 9 days
CPP [Member]
Mortgage and notes payable		$ 84.5	$ 84.9
Weighted average interest rate		1.83%	3.25%
Weighted average remaining term (Month)	[1]	58 months 3 days	30 months
Other Institutional Joint Ventures [Member]
Mortgage and notes payable	[2]	$ 169.5	$ 0.0
Weighted average interest rate	[2]	1.63%	0.00%
Weighted average remaining term (Month)	[1],[2]	6 months
Other Joint Venture Programs [Member]
Mortgage and notes payable	[2]	$ 402.9	$ 423.4
Weighted average interest rate	[2]	3.58%	3.41%
Weighted average remaining term (Month)	[1],[2]	86 months	86 months 21 days

[1] Includes extension options

[2] The joint ventures assumed an aggregate $191.5 million of secured debt (including a fair market value adjustment of $0.8 million) in connection with the Merger.